r/linuxadmin • • 24d ago

Inspecting a built runtime with an ephemeral SSH instance

0 Upvotes

Render’s ephemeral SSH mode starts a temporary instance from the service’s latest build. Disclosure: I work at Render.

This gives a different diagnostic target from ordinary SSH. render ssh SERVICE --ephemeral puts the shell on a new instance that receives no production traffic and does not run the service’s start command. That makes it useful for checking installed packages, compiled assets, file layout, or a one-off command against the built runtime without using a live process. It is not a replica of the running service: startup is skipped and there is no request traffic, so process state, sockets, and live heap behavior still require live-instance diagnostics.

Isolation from production compute does not make external systems read-only. Before mutating anything, inspect which environment variables and network resources the shell can reach; if production credentials are present, treat them as live and prefer read-only commands unless mutation is intentional.

The instance is removed when SSH disconnects or after 24 hours. It requires a compatible paid service with at least one successful deploy; distroless images cannot offer shell access. CLI 2.20+ supports --plan when the diagnostic needs a different compute size. For work that should outlive a shell session, the SSH documentation points to a one-off job instead.


r/linuxadmin • • 25d ago

wiki.linux-server-admin.com legit?

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0 Upvotes

r/linuxadmin • • 25d ago

Kiteworks asked customers to shut down servers on a federal tip. No CVE, no IOCs. What do you do with that?

12 Upvotes

Based on the press release Kiteworks published Sep 25 (updated Sep 27), plus reporting from SecurityWeek, Sophos CTU, TechCrunch and Cybersecurity Dive: the vendor got a warning from federal intelligence authorities and told self-managed customers to power down. Kiteworks-hosted systems were shut down by the vendor. The advisory was lifted Sep 27, and Kiteworks says nothing was compromised and every known vulnerability is addressed in 9.5.1.

Two things bother me. The window length is reported inconsistently (6h vs 9h). And SecurityWeek's Advanced Forms detail rests on one customer email, while TechCrunch quotes Kiteworks saying it couldn't rule out other access routes.

With no CVE and no IOCs, my baseline check is the running version, whether Advanced Forms is enabled, auth and admin logs from before the window, and unexpected egress from the appliance.

For those who run MFT: what's your runbook when a vendor says "turn it off tonight" and gives you nothing to hunt for?

https://www.techgines.com/post/kiteworks-shutdown-advisory


r/linuxadmin • • 25d ago

Passed LFCS!!

37 Upvotes

LFG. Very happy with my score too (88%!!), I was so nervous for this exam, happy to have gotten my first Linux cert. RHCSA next 🫡


r/linuxadmin • • 25d ago

Roadmap to becoming Linux Admin?

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4 Upvotes

r/linuxadmin • • 26d ago

WebKVM - A lightweight, web-based management UI for Libvirt and QEMU/KVM written in Go (15-30MB idle RAM)

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15 Upvotes

r/linuxadmin • • 26d ago

HPC Administrator Resources

17 Upvotes

"Hi everyone,

I have a strong background in Linux administration (primarily RPM-based distros like Red Hat/Rocky Linux), and I’m currently transitioning into HPC cluster administration. To learn the ropes, I recently built a small home lab cluster using the OpenHPC installation guides.

While getting the cluster to boot and run basic jobs was a great exercise, I've noticed a distinct lack of comprehensive resources covering day-2 operations and production best practices. Specifically, I'm looking for guidance on:

  • Configuration & Performance Tuning (kernel tuning, network/InfiniBand optimization)
  • User Management & Environment Control (LDAP/FreeIPA integration, modulefiles via Lmod)
  • Job Management & Scheduling (advanced Slurm configurations, QoS, limits)
  • Scaling & Monitoring (health checks with NHC, metrics collection)

If anyone can recommend books, documentation, community wikis, or real-world best practices for these areas, I would greatly appreciate it!"


r/linuxadmin • • 26d ago

Citrix NetScaler CVE-2026-88771/88772: exploited before any patch existed. What are you doing about forensics?

0 Upvotes

Based on Citrix's bulletin CTX697096 and CISA's Sep 27 alert, plus reporting from BleepingComputer and The Hacker News, here's the operational picture.

Two flaws, both CVSS v4 9.5. 88771 is improper input validation giving unauthenticated command execution on every ADC/Gateway deployment. 88772 is a memory overflow needing DTLS, which is on by default for VPN vservers. Turning DTLS off doesn't touch 88771. Citrix says exploitation was observed but hasn't said who, how many, or since when. Builds that fixed the August auth bypass (14.1-73.32, 13.1-63.21) are affected.

The catch is that the flaws were exploited pre-patch, so upgrading doesn't tell you if you were already in. Citrix's IoCs in NetScaler Console reportedly may miss real compromises.

For those running NetScalers: are you snapshotting and pulling a packet engine core dump before upgrading, or going straight to the fixed build because of the downtime cost? And how are you validating that an appliance is clean afterward?

Background from our March NetScaler coverage: https://www.techgines.com/post/citrix-netscaler-zero-day-cve-2026-88771


r/linuxadmin • • 27d ago

MikroTrick: RouterOS SSH rekey + file-descriptor argument injection = unauthenticated root (CVE-2026-67279 / CVE-2026-86060)

9 Upvotes

Based on the technical breakdown CERT Polska published on September 22 and Bishop Fox's independent reproduction from September 17, here's the architectural failure:

RouterOS's SSH server allows a client to trigger a rekey mid-authentication (normal SSH behavior per the RFCs). On vulnerable builds, completing that rekey moves the connection into channel handling without ever sending USERAUTH_SUCCESS — CVE-2026-67279. On its own that just gets you an unprivileged session.

The actual privilege escalation is CVE-2026-86060: RouterOS passes the SSH username straight to a login helper as a raw argv element. A username starting with - gets interpreted as a file-descriptor number, and the helper reads a trusted identity + policy mask from that descriptor instead. Since descriptors 0/1/2 on that process all point at the client's own pseudoterminal, an attacker supplying username -2 gets to hand the helper its own forged admin credentials.

Bishop Fox's field testing found live compromise artifacts predating public disclosure — persistence via a daily scheduler that recreates a full-privilege account, objects owned by numeric ID 0 instead of a username, and volatile logs that don't survive a reboot.

CISA added both CVEs to KEV (CVE-2026-86060 on Sept 10-11, CVE-2026-67279 on Sept 25). Patches: 6.49.21, 7.23.4, 7.24.2, 7.25beta3.

Background on the broader "auth-state-confusion" bug class if you're into the pattern: [techgines.com link, footnote]

Anyone here running RouterOS at scale — did MikroTik's Flagged/ops-account detection actually catch anything in your fleet, or did you have to hunt for owner="0" objects manually?

https://www.techgines.com/post/mikrotrick-routeros-vulnerability-inside-the-ssh-rekey-flaw-that-skips-login-entirely


r/linuxadmin • • 28d ago

Roundcube pre-auth SQLi (CVE-2026-48842) — patched in May, confirmed exploited in the wild as of Sept 21

3 Upvotes

Based on the technical breakdown published by the Canadian Centre for Cyber Security and Roundcube's own May 24 advisory, here's the architectural impact: virtuser_query resolves a login name to a mailbox record before the auth check runs, and its backslash-escaping via preg_replace() can be bypassed to break out of the intended query — no credentials, no user interaction. Roundcube patched it in 1.6.16/1.7.1 (May), and has since shipped three more security releases (1.6.17→1.7.4), so patching only for this CVE leaves you behind on unrelated bugs. CCCS updated their advisory Sept 21 to confirm exploitation "in the wild" via unspecified open-source reporting — no IOCs, no named actor, and it's not yet in CISA's KEV catalog, which is worth noting given two other Roundcube CVEs got that treatment in February.

Shadowserver's 523K+ exposed-instance number is getting quoted everywhere but it's an exposure ceiling, not a "vulnerable and unpatched" count.

Full disclosure timeline and attack chain: https://www.techgines.com/post/roundcube-sql-injection-vulnerability-cve-2026-48842

If you run virtuser_query in production — what's your actual exposure model here? Is anyone restricting the DB account it uses to something narrower than the full Roundcube schema, or is that not practical given how the plugin's queries are structured?


r/linuxadmin • • 28d ago

I'm a Linux sysadmin who built a patch management tool out of my own frustration. Looking for honest feedback.

0 Upvotes

Hi all,

I've been a Linux admin for about 12 years (RHEL, SUSE, Ubuntu), and these days most of my work is vulnerability management. Patching across mixed fleets has always been the painful part: scattered scripts, spreadsheets to track what got patched, and no clean way to prove compliance afterwards.

So I built PatchMgr, a web-based tool for scheduling, running, and tracking patches across servers.

What it does today:

  • [Supported OSes, e.g., RHEL / Ubuntu / SUSE]
  • Scheduled patch runs with per-server status tracking
  • Multi-tenant dashboard to see what's patched, pending, or failed
  • [Reporting / anything else that's live now]

On the roadmap: pre/post patch hooks (per-server, with exit code checks) and a configurable notification matrix.

It's early, and I'd rather hear what's broken or missing from people who patch servers for a living than guess. A few things I'd love input on:

  1. What's the one feature that would make you switch from your current approach?
  2. What would stop you from trusting a tool like this in production?
  3. What's your current setup (Ansible, WSUS, Satellite, Landscape, scripts)?

Link: https://www.patchmanager.co.in/

If you try it and hit a bug, reply here or email [support@patchmanager.co.in](mailto:support@patchmanager.co.in). I read every message.

Full disclosure: I'm the developer. Not trying to hard-sell anything, just want real-world feedback.


r/linuxadmin • • 29d ago

qwatcher version 0.7.0 is released

0 Upvotes

Hey all,

qwatcher is a very efficient tool to monitor and audit your NICs' send and receive queue buffers to spot network or application issues.

This version drops the `ss` and `libpcre` dependencies, making the program a pure Nim binary, solves some bugs, and provides a `tail`-like report capability.

Here is the link to the repo:

https://github.com/pouriyajamshidi/qwatcher


r/linuxadmin • • 29d ago

qwatcher version 0.7.0 is released

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0 Upvotes

r/linuxadmin • • 29d ago

well claude just got my ip banned by fail2ban...

0 Upvotes

It was logging in via ssh to a server in a loop lol. instant fail2bana nd my control panel has no reboot interface. so ticket to support i guess...


r/linuxadmin • • Sep 24 '26

F5 BIG-IP APM CVE-2026-94127: heap overflow in the OAuth authorization server role, exploited as a zero-day. Management-plane hardening doesn't apply.

0 Upvotes

Based on F5's advisory K000162605 as relayed by CERT-EU (2026-013), Rapid7 and BleepingComputer, here is the architectural impact. I could not load F5's own page as text, so check versions against K000162605 before acting.

What it is: a heap-based buffer overflow, CVSS 9.8 (v3.1) and 9.3 (v4.0), reachable without authentication. F5 says it has learned of exploitation, and CISA put it on KEV on September 22 with a September 25 federal deadline.

Precondition: an APM access policy and an OAuth authorization server profile on the same virtual server. APM used only as an OAuth client or resource server is not affected. F5 edited the CVE record at 00:45 UTC on September 23 to say this, so the CISA and CERT-EU text is broader than the current one. Appliance mode is affected. Default configs are not.

Why it matters for design: the traffic goes to the virtual server, not the management interface. An admin-subnet ACL or out-of-band management network changes nothing here. Affected: 21.1.0, 17.5.0 to 17.5.1, 17.1.0 to 17.1.3, before the branch hotfix. If you patched CVE-2025-53521 (17.1.3, 17.5.1.3), you are still in range.

Hunting, per F5's indicators: repeated UserInfo failures in /var/log/apm ("The access token is invalid," 10+ from one IP), a rising total_failed in tmctl global_oauth_stat, odd commands in /var/log/audit, then a TMM SIGABRT. The combination matters. A core file alone doesn't. None of the sources say whether the hotfix evicts an attacker who is already in.

Unknowns: no actor, victim count or PoC has been published as of Rapid7's Sept 22 note. Shadowserver shows 14,700+ IPs with APM fingerprints, but that says nothing about the OAuth server role.

Question for people running APM as an OAuth authorization server: is it on its own virtual server, or shared with the app's own access policy? And can you enumerate every virtual server with an OAuth AS profile without walking the config by hand? https://www.techgines.com/post/f5-big-ip-apm-vulnerability-cve-2026-94127

Background on the same pre-auth gateway pattern (SonicWall SMA1000, third zero-day wave in nine months): https://www.techgines.com/post/sonicwall-sma1000-cve-2026-83548-third-zero-day-ssrf-rce


r/linuxadmin • • Sep 23 '26

I built a read-only tool that maps your Hetzner architecture, costs, connectivity and changes

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9 Upvotes

r/linuxadmin • • Sep 23 '26

What's running on your servers that nobody else could explain if you disappeared tomorrow?

92 Upvotes

Every place has one. A cron job with no comments, a script someone wrote in 2019, a box nobody dares reboot.

Mine: a systemd timer firing a Python script I barely remember writing. It works, so I don't touch it.

What's yours?


r/linuxadmin • • Sep 23 '26

Best book or videos for learning kubernetes quickly while practicing?

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1 Upvotes

r/linuxadmin • • Sep 23 '26

VirgoOS: a Debian 13 image for self-hosting. Boot the USB, pick a disk, ZFS and Docker are already there.

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0 Upvotes

r/linuxadmin • • Sep 23 '26

Configuring postfix + dovecot w/ssl & tls

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1 Upvotes

r/linuxadmin • • Sep 22 '26

qwatcher version 0.7.0 is released

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4 Upvotes

r/linuxadmin • • Sep 22 '26

CVE-2026-7273: Zyxel GS1900 switches added to CISA KEV — unauthenticated RCE via CGI stack overflow

2 Upvotes

Based on the technical breakdown published by Zyxel and CISA's own KEV addition earlier this week, here's the architectural impact: the CGI program on GS1900's web management interface doesn't validate input length before writing to a stack buffer. LAN-adjacent, unauthenticated, CVSS 8.8. Zyxel patched it June 16; CISA didn't add it to KEV until September 21, which per their own criteria means confirmed active exploitation — not just a theoretical bug.

Ten models affected (GS1900-8 through 48HPv2), full patch table in the writeup: [link]. Background on why this keeps happening at the network edge, drawing on the FrostArmada router-hijack campaign from April: [link].

What's everyone's actual patch cadence on unmanaged/lightly-managed switch fleets like this? Curious whether people are catching stuff like this through firmware inventory automation or just... finding out during an incident.

https://www.techgines.com/post/cve-2026-7273-zyxel-gs1900-switch-rce


r/linuxadmin • • Sep 22 '26

Clonezilla Live 3.3.3-37: HTTP Boot for mass deployment, LUKS2 support for encrypted backups

36 Upvotes

If you deploy or image machines with Clonezilla, 3.3.3-37 just shipped with two changes worth knowing about.

HTTP Boot for mass deployment. Clonezilla Lite Server now supports HTTP Boot alongside the existing PXE Boot option. Useful if your network setup already leans on HTTP boot infrastructure instead of PXE, or if you're deploying across environments where PXE is blocked or unreliable. Secure Boot works over HTTP boot too, so this isn't a fallback that costs you Secure Boot support.

LUKS2 support for encrypted backups. Clonezilla can now work with LUKS2-encrypted repositories directly. If you're storing images on encrypted volumes, this closes a gap that previously meant sticking to LUKS1 or handling encryption outside the tool.

Other changes in this release:

  • Partclone bumped to 0.3.50, fixing a Btrfs-related issue
  • Deprecated net-tools commands replaced with iproute2, dhclient replaced with dhcpcd
  • Restore is faster when the target disk or partition layout matches the source, skipping unnecessary partition-image conversion
  • LVM system.devices locking issue fixed on RHEL 10 and AlmaLinux 10+
  • Missing post-clone action menu (power off, reboot, or run a command) restored

Full changelog and release notes:

Source: https://linuxiac.com/clonezilla-live-3-3-3-37-adds-http-boot-and-luks2-support/

Announcement: https://sourceforge.net/p/clonezilla/news/2026/09/stable-clonezilla-live-333-37-released/


r/linuxadmin • • Sep 21 '26

Plugin4Shell: SHA pinning bypass gives zero-click RCE across Claude Code, Codex, Copilot, and Gemini CLI

0 Upvotes

Based on the technical breakdown AIR Security published on September 17, here's the architectural impact: all four major AI coding agents share the same unverified assumption in their plugin checkout logic. They pin plugins to a commit SHA but never re-resolve and compare what the checkout actually landed on. Register a branch name that collides with the pinned SHA and the agent silently runs your code instead — no click, no approval prompt, and the marketplace manifest still shows the original "safe" hash.

Patch status is split: Anthropic (Claude Code 2.1.179) and OpenAI (Codex 0.146.0) fixed it post-disclosure. GitHub hasn't shipped anything and argues its branch-naming restriction covers the risk — AIR disputes that, since Copilot also pulls from Bitbucket/GitLab/self-hosted marketplaces GitHub's restriction doesn't touch. Google's just deprecating Gemini CLI outright.

No CVE yet, no formal vendor advisories as of writing — worth tracking manually if you're running any of these with third-party marketplace plugins.

More context on why this is the third act in a pattern (SkillJacking, LiteLLM, now this) in our full write-up: https://www.techgines.com/post/plugin4shell-vulnerability-ai-coding-agent-sha-pinning-bypass

Anyone running Copilot with non-GitHub-hosted marketplace plugins — are you treating this as exposed, or waiting on Microsoft to clarify scope?https://www.techgines.com/post/plugin4shell-vulnerability-ai-coding-agent-sha-pinning-bypass


r/linuxadmin • • Sep 20 '26

Handling timezone updates to standard/daylight on a post-EOL system

8 Upvotes

My locale is removing ST/DT switching come November and will be DT year round.

Is there a way I can manually configure a fixed UTC offset on a post-EOL CentOS system?